def is_subsequence(a, b):
seq = iter(b)
return all(i in seq for i in a)
print(is_subsequence('ad', 'abcd'))
print(is_subsequence('adc', 'abcd'))
ZGVmIGlzX3N1YnNlcXVlbmNlKGEsIGIpOgogICAgc2VxID0gaXRlcihiKQogICAgcmV0dXJuIGFsbChpIGluIHNlcSBmb3IgaSBpbiBhKQoKcHJpbnQoaXNfc3Vic2VxdWVuY2UoJ2FkJywgJ2FiY2QnKSkKcHJpbnQoaXNfc3Vic2VxdWVuY2UoJ2FkYycsICdhYmNkJykp